The present invention concerns an internal combustion engine having an induction conduit of for the induction of fresh air, and more particularly, an engine in which a cylinder head cover covers a camshaft space of the internal combustion engine at the top portion, with a section of the induction conduit extending over the cylinder head cover.
An internal combustion engine is shown in DE-PS 32 17 633. In addition, engine space ventilation is known for an internal combustion engine associated with an exhaust gas turbocharger as shown in DE-GM 89 00 612. The ventilation described therein takes place via ducts located within the engine casing and by a conduit external to the engine.
An object of the present invention is to provide internal combustion engine space ventilation, which is as simple as possible and is as operationally reliable as possible.
That object has been achieved according to the present invention by providing that the induction conduit section has at least one connection stub pipe protruding through an opening in the cylinder head cover into the camshaft space. The connection between the camshaft space and the induction conduit therefore takes place without a special conduit so that, on one hand, simple engine space ventilation is achieved because of the small number of parts and because of the short paths involved. On the other hand, the operational reliability of the invention is ensured because the hot ventilation gases are only subject to a small amount of cooling on the short path from the engine space to the induction conduit so that freezing of the connection is avoided. Because the engine space ventilation is necessarily connected during the fitting of the induction conduit, fitting is also simplified.
In one embodiment of the invention, a ring-shaped sealing element is pressed into each opening of the cylinder head cover in order to seal the camshaft space from the space external to the engine. The sealing element is in contact with the outside of the connection stub pipe by a sealing lip. During assembly, the connection stub pipe is pushed in a simple manner through the sealing element provided in the opening. The sealing element is then in sealing contact with the connection stub pipe so that no additional connecting elements, such as hose clips, are necessary for sealing.
A further advantageous feature of the present invention is that the cylinder head cover has at least one raised section which encloses a ventilation space separated from the camshaft space by a precipitation plate, with the connection stub pipe being connected to the ventilation space. The provision of a precipitation plate in the cylinder head cover as a protecting plate substantially prevents the oil thrown up by a camshaft from reaching the connection stub pipe. A ventilation space is created through which ventilation gases flow almost exclusively and which is separated from the camshaft space by the precipitation plate. By suitable dimensioning of the ventilation space, oil penetrating with the ventilation gases can be precipitated on the walls of the ventilation space. The cross-section of the connection stub pipe is also increased such that the flow velocity of the ventilation gases is very low so that only a little oil is entrained into the induction conduit by the gases.
According to yet another advantageous aspect of the present invention, a lower wall section of the induction conduit is doubled to form a ventilation duct. The ventilation duct is connected via a gap to the induction conduit at the downstream end of the section. The ventilation gases are screened thereby from the suction effect of the static pressure, which is very low at full-load operation. This low static pressure occurs because of the high velocity of the fresh air flowing through the induction conduit. The ventilation duct therefore represents a substantially still zone in which the oil entrained in the ventilation gases is precipitated and can then flow back into the crankcase via the connection stub pipes. Further on in the flow direction, the ventilation gases pass via the gap at the end of the wall section into the induction conduit.
A still further advantage of the present invention resides in the fact that the lower wall section of the induction conduit is offset towards the center of the induction conduit in the region of the connection stub pipes. In addition, the connection stub pipes are accommodated in a cap which is located within the extent of the induction conduit and covers the lower wall section so that the wall section and the cap form the boundaries of the ventilation duct. The wall section offset towards the center of the induction conduit reduces the cross-sectional area of the induction conduit on one section so that pulsations, which can occur in the induction conduit at full-load operation because of the flow through the valves, are damped. This prevents the suction effect of the vacuum regions formed locally by pulsations from acting on the oil containing ventilation gases from the crankcase ventilation.
Advantageously, the gap at the downstream end of the section can also be located at a distance from the cap. Consequently, the end of the section forms an oil weir at which is substantially precipitated and collected the rest of the entrained oil from the ventilation gases and which restrains the separated oil from flowing out into the induction conduit. Overall, the hereinafter described currently contemplated embodiments of the present invention substantially prevent oil from the crankcase ventilation from entering the induction conduit so that the oil consumption is reduced. In addition, the formation of blue smoke and HC emissions is reduced during engine combustion so that, because of the decreased load on it, the life of a catalyzer provided in an exhaust gas system can be extended.
Finally, it is possible to prevent a hot-wire air meter located in the induction conduit from being subjected to oil thus avoiding the erroneous recognition of the air mass induced, due to the presence of oil.